Multifunctional terbium iron borate magnetic refrigeration crystal material as well as preparation method and application thereof

Abstract

The invention discloses a multifunctional terbium iron borate magnetic refrigeration crystal material as well as a preparation method and application thereof, and the multifunctional terbium iron borate magnetic refrigeration crystal material is prepared by taking a terbium-containing compound A, an iron-containing compound A and a boron-containing compound A as raw materials and adopting a fluxing agent method. Experiments prove that the multifunctional terbium iron borate magnetic refrigeration crystal material not only has a traditional magnetothermal effect but also has a diamagnetothermal effect in a low-temperature region below 60K, and has a very strong anisotropic magnetothermal effect, so that the multifunctional terbium iron borate magnetic refrigeration crystal material can have a wider application scene; for example, development and application of rotary magnetic refrigerators and heat dissipation electronic devices are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic materials, and in particular to a multifunctional terbium iron borate magnetic refrigeration crystal material and a preparation method and application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] At present, the mainstream household refrigeration technology in my country is still the air compression refrigeration technology using Freon as the refrigerant, and its efficiency is only 5-10% of the Carnot cycle. Since it uses hydrochlorofluorocarbons (HCFCs) as refrigerants, it has caused great resistance to the implementation of the country's energy conservation and emission reduction actions, and it is in urgent need of updating to a new environmentally friendly refrigeration technology. In recent years, magnetic refrigeration technology based on magnetocaloric effect, compared with traditional gas compression refrigeration technology, has the advantages of high efficiency, energy saving, green environmental protection, and small size because it uses the method of applying and removing magnetic fields to solid refrigerants. It is very likely to become a new generation of refrigeration technology. In particular, rotating some materials with anisotropic magnetocaloric effect under a constant magnetic field can also obtain a higher rotary magnetic refrigeration effect, while also reducing the additional energy consumption caused by the rising and falling magnetic fields. Therefore, rotary magnetic refrigeration technology has recently received widespread attention. According to the magnetic entropy change (-ΔS M ) symbol, the magnetocaloric effect can be divided into two types: one is that the magnetic field decreases under adiabatic conditions, causing the temperature of the magnetic refrigeration material to drop, and the other is that the magnetic entropy change (-ΔS M >0) of the traditional magnetocaloric effect (CMCE), and the other is the temperature rise of the magnetic refrigeration material caused by the decrease of the magnetic field under adiabatic conditions, with a positive magnetic entropy change (-ΔS M <0). The traditional magnetocaloric effect and the inverse magnetocaloric effect can be applied in magnetic refrigeration technology and heat dissipation electronic devices respectively, and their application prospects are very broad. In summary, it can be seen that it is of great significance to explore multifunctional magnetic refrigeration materials with traditional magnetocaloric effect, inverse magnetocaloric effect and anisotropic magnetocaloric effect, and make them suitable for multi-scenario applications with comprehensive extreme conditions, such as military industry, aerospace, large scientific equipment, etc. However, there are relatively few studies on multifunctional magnetic refrigeration materials. Summary of the Invention

[0004] Therefore, based on the above background, the present invention provides a multifunctional terbium iron borate magnetic refrigeration crystal material and its preparation method and application. The multifunctional terbium iron borate magnetic refrigeration crystal material has both traditional magnetocaloric effect and reverse magnetocaloric effect in the low temperature region below 60K, so that it can meet more application scenarios.

[0005] The technical solution provided by the present invention is:

[0006] A multifunctional terbium iron borate magnetic refrigeration crystal material, whose chemical formula is TbFe3(BO3)4, belongs to the trigonal crystal system, and the space group is R32 (No.155). Specifically, the unit cell parameters are: α=β=90°, γ=120°, Z=3.

[0007] Furthermore, the multifunctional terbium iron borate magnetic refrigeration crystal material has a traditional magnetocaloric effect at a temperature above 35K and an inverse magnetocaloric effect at a temperature below 35K.

[0008] Based on the same inventive concept, the present invention also provides a method for preparing a multifunctional terbium iron borate magnetic refrigeration crystal material, which is characterized by comprising the following steps:

[0009] (1) Preparation of terbium iron borate polycrystalline compound

[0010] After uniformly mixing the terbium-containing compound A, the iron-containing compound A and the boron-containing compound A, the mixture is heated to 800-1500° C., kept warm for a certain period of time, and cooled to obtain a terbium iron borate polycrystalline compound.

[0011] (2) Preparation of terbium iron borate crystals

[0012] The terbium iron borate polycrystalline compound obtained in step (1) and the flux are mixed evenly, placed in a crucible, placed in a crystal growth furnace, heated to 800-1500°C, kept warm for a certain period of time, cooled to 800-850°C in two stages, and finally cooled to room temperature; then, the crucible containing the terbium iron borate crystal and flux mixture is immersed in hot dilute nitric acid and subjected to ultrasonic vibration to separate the terbium iron borate crystals.

[0013] Specifically, the two-stage cooling operation is as follows:

[0014] First, slowly cool down to 900-1000°C at a rate of 3-20°C / hour, and then cool down to 800-850°C at a rate of 0.1-0.3°C / hour.

[0015] Furthermore, the terbium-containing compound A is a terbium-containing oxide; the iron-containing compound A is an iron-containing oxide; and the boron-containing compound A is a boron-containing oxide.

[0016] Furthermore, the terbium-containing compound A is selected from Tb4O7, the iron-containing compound is selected from Fe2O3, and the boron-containing compound A is selected from B2O3.

[0017] Furthermore, the terbium-containing compound A, the iron-containing compound, and the boron-containing compound A are mixed in a molar ratio of atomic Tb, Fe, and B of 1:3:4.

[0018] Furthermore, the flux is composed of a boron-containing compound B, a terbium-containing compound B, and a bismuth-molybdenum compound in a molar ratio of 15:3:5;

[0019] The boron-containing compound B is selected from B2O3, the terbium-containing compound B is selected from Tb4O7, and the bismuth-molybdenum compound is selected from Bi2Mo3O 12 .

[0020] Furthermore, in step (2), the terbium iron borate polycrystalline compound and the flux are mixed in a mass ratio of 1:3; for example, if the terbium iron borate polycrystalline compound is 15 g, the mass of the flux is 45 g.

[0021] Furthermore, the mass fraction of HNO3 in the hot dilute nitric acid in step 2) is 10-25%; illustratively, the mass fraction can be 12%, 14%, 16%, 18%, 20%, 22%, 24%, etc., preferably 20%.

[0022] Furthermore, the crucible in step 2) is a platinum crucible.

[0023] Based on the same inventive concept, the present invention also provides the above-mentioned multifunctional terbium iron borate magnetic refrigeration crystal material, the application of the multifunctional terbium iron borate magnetic refrigeration crystal material prepared by the above-mentioned method for preparing a multifunctional terbium iron borate magnetic refrigeration crystal material in the field of magnetic refrigeration, and the use of the multifunctional terbium iron borate magnetic refrigeration crystal material as a magnetic refrigeration material in an ambient temperature of 2-60K.

[0024] Furthermore, at temperatures below 35K, it can be used as a magnetic refrigeration material for heat dissipation in electronic devices; or at temperatures below 60K, it can be used as a magnetic refrigeration material in rotary magnetic refrigerators.

[0025] The above technical solution has the following beneficial effects:

[0026] Experiments have shown that when the direction of the ambient magnetic field is parallel to the

[001] orientation of the crystal and the magnetic field strength increases from 0 kOe to 70 kOe, the isothermal magnetic entropy change of the terbium iron borate magnetic refrigeration crystal material of the present invention reaches a maximum negative value of -4.5 J / kgK at 41 K, exhibiting a traditional magnetocaloric effect; when the ambient magnetic field strength increases from 0 kOe to 40 kOe, the isothermal magnetic entropy change reaches a maximum positive value of +4.2 J / kgK at 13 K, exhibiting an inverse magnetocaloric effect.

[0027] The terbium iron borate magnetic refrigeration crystal of the present invention exhibits a strong anisotropic magnetocaloric effect: when the direction of the ambient magnetic field is parallel to the

[110] crystal orientation of the crystal, and the magnetic field strength increases from 0 kOe to 70 kOe, the isothermal magnetic entropy changes corresponding to the conventional magnetocaloric effect and the inverse magnetocaloric effect are only -0.09 J / kgK and +0.36 J / kgK, respectively, which are much smaller than the isothermal magnetic entropy change values ​​when the magnetic field is parallel to the

[001] crystal orientation. Under a constant magnetic field of 70 kOe, the rotational magnetic entropy change obtained by rotating the terbium iron borate magnetic refrigeration crystal from the

[001] crystal orientation to the

[110] crystal orientation reaches a maximum negative value of -4.50 J / kgK at 41 K. Under a constant magnetic field of 40 kOe, the positive rotational magnetic entropy change obtained by rotating from the

[001] crystal orientation to the

[110] crystal orientation reaches a maximum positive value of 4.12 J / kgK at 13 K.

[0028] Therefore, the terbium iron borate magnetic refrigeration crystal of the present invention has both traditional magnetocaloric effect and reverse magnetocaloric effect in the low temperature region below 60K, which enables it to have a wider range of application scenarios, such as the development and application of rotary magnetic refrigerators and heat dissipation electronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 (a) is the X-ray diffraction pattern of the TbFe3(BO3)4 polycrystalline compound prepared in Example 1; (b) is the X-ray diffraction pattern of the TbFe3(BO3)4 crystal prepared in Example 1 along the (110) crystal plane; (c) is the Y 0.5 Bi 0.5 The diffraction standard line of Fe3(BO3)4 compound in the JCPDS crystal database (No.87-1764). The inset of Figure (b) is a physical image of TbFe3(BO3)4 crystal prepared in Example 1.

[0030] Figure 2 These are the thermomagnetic curves of the TbFe3(BO3)4 crystal prepared in Example 1 along the

[001] and

[110] crystal axes under zero magnetic field cooling (ZFC) and with magnetic field cooling (FC).

[0031] Figure 3 Magnetic hysteresis loops of the TbFe3(BO3)4 crystal prepared in Example 1 at temperatures of 1.8 K and 30 K: (a) along the

[001] crystal axis (magnetic field parallel to the c-axis); (b) along the

[110] crystal axis (magnetic field perpendicular to the c-axis).

[0032] Figure 4Isothermal magnetization curve of the TbFe3(BO3)4 crystal prepared in Example 1 in the temperature range of 2-70K: (a) along the

[001] crystal axis (magnetic field parallel to the c-axis); (b) along the

[110] crystal axis (magnetic field perpendicular to the c-axis).

[0033] Figure 5 Isothermal magnetic entropy change curve of the TbFe3(BO3)4 crystal prepared in Example 1 in the temperature range of 20-70K and the magnetic field of 2-70kOe: (a) along the

[001] crystal axis (magnetic field parallel to the c-axis); (b) along the

[110] crystal axis (magnetic field perpendicular to the c-axis).

[0034] Figure 6 This is the rotational magnetic entropy change curve of the TbFe3(BO3)4 crystal prepared in Example 1 when the magnetic field is rotated from parallel to the

[001] crystal axis to parallel to the

[110] crystal axis. DETAILED DESCRIPTION

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0036] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0037] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0038] Example 1: Preparation of TbFe3(BO3)4 crystals by a flux method, specifically comprising the following steps:

[0039] (1) Preparation of terbium iron borate polycrystalline compound

[0040] Tb4O7, Fe2O3, and B2O3 were uniformly mixed according to the molar ratio of atomic Tb:Fe:B of 1:3:4, placed in a corundum crucible and placed in a muffle furnace. In an oxygen environment, the temperature was raised to 1000°C at a constant rate of 3°C / min, then kept at 1000°C for 3 days, and finally cooled to room temperature in the furnace to obtain a terbium iron borate (TbFe3(BO3)4) polycrystalline compound;

[0041] (2) Preparation of terbium iron borate crystals

[0042] Take Bi2Mo3O according to the molar ratio of 5:15:312 , B2O3, and Tb4O7 are mixed evenly.

[0043] The terbium iron borate polycrystalline compound obtained in step (1) and the flux are mixed uniformly in a mass ratio of 1:3 and placed in a platinum crucible. The platinum crucible is placed in a crystal growth furnace, heated to 1000°C at a uniform rate of 3°C / min, and then kept at 1000°C for 24 hours. Thereafter, the temperature is slowly lowered to 962°C at a uniform rate of 3.8°C / hour, and then lowered to 850°C at a uniform rate of 0.15°C / hour, and then cooled to room temperature with the furnace to obtain a mixture of terbium iron borate crystals and flux;

[0044] The platinum crucible containing the terbium iron borate crystal and flux mixture was immersed in hot dilute nitric acid at 80 ° C and ultrasonically shaken for 3-5 days to separate the 1.59×2.09×1.5mm 3 The TbFe3(BO3)4 crystal of the size is a multifunctional terbium iron borate magnetic refrigeration crystal material.

[0045] The TbFe3(BO3)4 crystals prepared above were characterized and tested, and the results are shown below.

[0046] 1) Crystal structure characterization test

[0047] The structure of TbFe3(BO3)4 polycrystalline compound and crystal (110) plane obtained by X-ray diffraction analyzer was characterized, and the XRD pattern obtained was as follows: Figure 1 The diffraction peak positions of the polycrystal and the crystal are consistent with the standard spectrum. After analysis, the TbFe3(BO3)4 crystal obtained in Example 1 belongs to the trigonal system, the space group is R32 (No.155), and the unit cell parameters are: α=β=90°, γ=120°, Z=3.

[0048] 2) Magnetic performance test

[0049] The magnetic characterization and magnetocaloric effect of the TbFe3(BO3)4 crystal obtained in Example 1 were studied using a Quantum Design SQUID-VSM vibrating sample magnetometer in the temperature range of 2-300K and the magnetic field range of 0-70kOe:

[0050] The zero field cooling (ZFC) and field cooling (FC) thermomagnetic curves of the TbFe3(BO3)4 crystal obtained in Example 1 along the

[001] and

[110] crystal axes in the temperature range of 2-300K and the magnetic field range of 0-70kOe are as follows: Figure 2The results show that the ZFC curves and FC curves in the two crystal axis directions completely overlap, with no obvious thermal hysteresis and strong magnetocrystalline anisotropy. An antiferromagnetic-paramagnetic phase transition occurs around 38.2K.

[0051] Figure 3 The hysteresis loops of the TbFe3(BO3)4 crystal obtained in Example 1 along the

[001] and

[110] crystal axes at temperatures of 1.8 K and 10 K are shown. The results show that the hysteresis loops along the two crystal axes completely overlap, with no hysteresis phenomenon, and significant magnetocrystalline anisotropy.

[0052] Figure 4 The isothermal magnetization curves of the TbFe3(BO3)4 crystal obtained according to Example 1 along the

[001] and

[110] crystal axes in the 2-70K temperature range are shown. The results show that the magnetization curve along the

[001] crystal axis exhibits a step-like transition in the 2-28K temperature range and the 30-60kOe magnetic field range, while the magnetization curve along the

[110] crystal axis exhibits a linear relationship with the magnetic field in the 3-70K temperature range and the 0-90kOe magnetic field range. The magnetization intensity along the

[110] crystal axis is much smaller than that along the

[001] crystal axis, indicating strong magnetocrystalline anisotropy.

[0053] Figure 5 The low-temperature variable-field magnetic entropy change curves of the TbFe3(BO3)4 crystal along the

[001] and

[110] crystal axis directions obtained according to Example 1 within the magnetic field variation range of H = 0-70kOe are shown. The results show that both crystal axis directions have positive magnetic entropy change (inverse magnetocaloric effect) below 35K and negative magnetic entropy change (conventional magnetocaloric effect) above 35K. When the magnetic field is along the

[001] crystal direction, under the magnetic field variation of ΔH = 40kOe, the maximum variable-field positive magnetic entropy change is +4.23J / kg K, and under the magnetic field variation of ΔH = 70kOe, the maximum variable-field negative magnetic entropy change is -4.56J / kg K. When the magnetic field is along the

[110] crystal direction, under the magnetic field variation of ΔH = 70kOe, the maximum variable-field positive magnetic entropy change is +0.36J / kg K, and the maximum variable-field negative magnetic entropy change is -0.09J / kg K. There is a strong anisotropic magnetocaloric effect between the

[001] and

[110] crystal axes.

[0054] Figure 6The rotational magnetic entropy change curve of the TbFe3(BO3)4 crystal obtained in Example 1 is obtained by rotating the magnetic field along the

[001] to

[110] crystal axis direction within the constant magnetic field range of H = 0-70kOe. The results show that when the magnetic field is 40kOe, the maximum rotational magnetic entropy change of the TbFe3(BO3)4 crystal reaches a positive maximum value (+4.12J / kg K) at 13K. When the magnetic field is 70kOe, the maximum rotational magnetic entropy change of the TbFe3(BO3)4 crystal reaches a negative maximum value (-4.50J / kg K) at 41K.

[0055] Example 2:

[0056] The preparation of TbFe3(BO3)4 crystals by the flux method includes the following steps:

[0057] Tb4O7, Fe2O3, and B2O3 were added and mixed uniformly according to the molar ratio of Tb:Fe:B of 1:3:4, placed in a corundum crucible and placed in a muffle furnace. In an oxygen environment, the temperature was raised to 1000°C at a constant rate of 3°C / min, then kept at 1000°C for 3 days, and finally cooled to room temperature with the furnace to obtain a TbFe3(BO3)4 polycrystalline compound.

[0058] Bi2Mo3O 12 , B2O3, and Tb4O7 are fully mixed in a molar ratio of 5:15:3 to obtain a flux;

[0059] The obtained TbFe3(BO3)4 polycrystalline compound and flux were mixed in a mass ratio of 1:3 and placed in a platinum crucible. The platinum crucible was placed in a crystal growth furnace and heated to 1000°C at a uniform rate of 3°C / min, and then kept at 1000°C for 2 hours. Thereafter, the temperature was slowly lowered to 962°C at a uniform rate of 19°C / hour, and then to 850°C at a uniform rate of 0.25°C / hour. After cooling to room temperature in the furnace, a mixture of terbium iron borate crystals and flux was obtained.

[0060] The platinum crucible containing the terbium iron borate crystals and flux mixture is immersed in hot dilute nitric acid at 80°C and subjected to ultrasonic vibration for 3-5 days to separate and obtain TbFe3(BO3)4 crystals.

[0061] The TbFe3(BO3)4 crystals obtained in Example 2 were characterized by XRD, and the results were basically consistent with those in Example 1.

[0062] Example 3

[0063] The preparation of TbFe3(BO3)4 crystals by the flux method includes the following steps:

[0064] Tb4O7, Fe2O3, and B2O3 were added and mixed uniformly according to the molar ratio of Tb:Fe:B of 1:3:4, placed in a corundum crucible and placed in a muffle furnace. In an oxygen environment, the temperature was raised to 1000°C at a constant rate of 3°C / min, then kept at 1000°C for 3 days, and finally cooled to room temperature with the furnace to obtain a TbFe3(BO3)4 polycrystalline compound.

[0065] Bi2Mo3O 12 , B2O3, and Tb4O7 are fully mixed in a molar ratio of 5:15:3 to obtain a flux;

[0066] The obtained TbFe3(BO3)4 polycrystalline compound and flux were mixed in a mass ratio of 1:3 and placed in a platinum crucible. The platinum crucible was placed in a crystal growth furnace and heated to 1000°C at a uniform rate of 4°C / min, and then kept at 1000°C for 24 hours. Thereafter, the temperature was slowly lowered to 962°C at a uniform rate of 19°C / hour, and then to 850°C at a uniform rate of 0.25°C / hour. After cooling to room temperature in the furnace, a mixture of terbium iron borate crystals and flux was obtained.

[0067] The platinum crucible containing the terbium iron borate crystals and flux mixture is immersed in hot dilute nitric acid at 80°C and subjected to ultrasonic vibration for 3-5 days to separate and obtain TbFe3(BO3)4 crystals.

[0068] The TbFe3(BO3)4 crystals obtained in Example 3 were characterized by XRD, and the results were basically consistent with those in Example 1.

[0069] Example 3

[0070] The preparation of TbFe3(BO3)4 crystals by the flux method includes the following steps:

[0071] Tb4O7, Fe2O3, and B2O3 were added and mixed uniformly according to the molar ratio of Tb:Fe:B of 1:3:4, placed in a corundum crucible and placed in a muffle furnace. In an oxygen environment, the temperature was raised to 1000°C at a constant rate of 3°C / min, then kept at 1000°C for 3 days, and finally cooled to room temperature with the furnace to obtain a TbFe3(BO3)4 polycrystalline compound.

[0072] Bi2Mo3O 12 , B2O3, and Tb4O7 are fully mixed in a molar ratio of 5:15:3 to obtain a flux;

[0073] The obtained TbFe3(BO3)4 polycrystalline compound and flux were mixed in a mass ratio of 1:3 and placed in a platinum crucible. The platinum crucible was placed in a crystal growth furnace and heated to 1000°C at a uniform rate of 4°C / min. The temperature was then kept at 1000°C for 24 hours. Thereafter, the temperature was slowly lowered to 962°C at a uniform rate of 19°C / hour, and then to 850°C at a uniform rate of 0.20°C / hour. The mixture was then cooled to room temperature in the furnace to obtain a mixture of terbium iron borate crystals and flux.

[0074] The platinum crucible containing the terbium iron borate crystals and flux mixture is immersed in hot dilute nitric acid at 80°C and subjected to ultrasonic vibration for 3-5 days to separate and obtain TbFe3(BO3)4 crystals.

[0075] The TbFe3(BO3)4 crystals obtained in Example 3 were characterized by XRD, and the results were basically consistent with those in Example 1.

[0076] Example 4

[0077] The preparation of TbFe3(BO3)4 crystals by the flux method includes the following steps:

[0078] Tb4O7, Fe2O3, and B2O3 were added and mixed uniformly according to the molar ratio of Tb:Fe:B of 1:3:4, placed in a corundum crucible and placed in a muffle furnace. In an oxygen environment, the temperature was raised to 1000°C at a constant rate of 3°C / min, then kept at 1000°C for 3 days, and finally cooled to room temperature with the furnace to obtain a TbFe3(BO3)4 polycrystalline compound.

[0079] Bi2Mo3O 12 , B2O3, and Tb4O7 are fully mixed in a molar ratio of 5:15:3 to obtain a flux;

[0080] The obtained TbFe3(BO3)4 polycrystalline compound and flux were mixed in a mass ratio of 1:3 and placed in a platinum crucible. The platinum crucible was placed in a crystal growth furnace and heated to 1000°C at a uniform rate of 4°C / min, and then kept at 1000°C for 24 hours. Thereafter, the temperature was slowly lowered to 962°C at a uniform rate of 5°C / hour, and then to 850°C at a uniform rate of 0.25°C / hour. After cooling to room temperature in the furnace, a mixture of terbium iron borate crystals and flux was obtained.

[0081] The platinum crucible containing the terbium iron borate crystals and flux mixture is immersed in hot dilute nitric acid at 80°C and subjected to ultrasonic vibration for 3-5 days to separate and obtain TbFe3(BO3)4 crystals.

[0082] The TbFe3(BO3)4 crystals obtained in Example 4 were characterized by XRD, and the results were basically consistent with those in Example 1.

[0083] Example 5

[0084] The preparation of TbFe3(BO3)4 crystals by the flux method includes the following steps:

[0085] Tb4O7, Fe2O3, and B2O3 were added and mixed uniformly according to the molar ratio of Tb:Fe:B of 1:3:4, placed in a corundum crucible and placed in a muffle furnace. In an oxygen environment, the temperature was raised to 1000°C at a constant rate of 3°C / min, then kept at 1000°C for 3 days, and finally cooled to room temperature with the furnace to obtain a TbFe3(BO3)4 polycrystalline compound.

[0086] Bi2Mo3O 12 , B2O3, and Tb4O7 are fully mixed in a molar ratio of 5:15:3 to obtain a flux;

[0087] The obtained TbFe3(BO3)4 polycrystalline compound and flux were mixed in a mass ratio of 1:3 and placed in a platinum crucible. The platinum crucible was placed in a crystal growth furnace and heated to 1000°C at a uniform rate of 4°C / min, and then kept at 1000°C for 24 hours. Thereafter, the temperature was slowly lowered to 962°C at a uniform rate of 7°C / hour, and then to 850°C at a uniform rate of 0.25°C / hour. After cooling to room temperature in the furnace, a mixture of terbium iron borate crystals and flux was obtained.

[0088] The platinum crucible containing the terbium iron borate crystals and flux mixture is immersed in hot dilute nitric acid at 80°C and subjected to ultrasonic vibration for 3-5 days to separate and obtain TbFe3(BO3)4 crystals.

[0089] The TbFe3(BO3)4 crystals obtained in Example 4 were characterized by XRD, and the results were basically consistent with those in Example 1.

[0090] Compared with Example 1, Examples 2 to 5 have different heating rates and cooling rates in the preparation steps of terbium iron borate crystals, and the sizes of the TbFe3(BO3)4 crystals finally obtained are different.

[0091] The present invention and its embodiments are described above. Such description is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. In short, if a person skilled in the art is inspired by the above, and does not deviate from the purpose of the present invention, without inventive design, a structure and embodiment similar to the technical solution should fall within the scope of protection of the present invention.

Claims

1. A multifunctional terbium iron borate magnetic refrigeration crystal material, characterized in that: Its chemical formula is TbFe3(BO3)4, it belongs to the trigonal crystal system and its space group is R32 (No.155).

2. The multifunctional terbium iron borate magnetic refrigeration crystal material according to claim 1, characterized in that: The multifunctional terbium iron borate magnetic refrigeration crystal material has a traditional magnetocaloric effect at a temperature above 35K and an inverse magnetocaloric effect at a temperature below 35K.

3. The method for preparing a multifunctional terbium iron borate magnetic refrigeration crystal material according to claim 1 or 2, characterized in that: The steps include: (1) Preparation of terbium iron borate polycrystalline compound After uniformly mixing the terbium-containing compound A, the iron-containing compound A and the boron-containing compound A, the mixture is heated to 800-1500° C., kept at this temperature for a certain period of time, and cooled to obtain a terbium iron borate polycrystalline compound. (2) Preparation of terbium iron borate crystals The terbium iron borate polycrystalline compound obtained in step (1) and the flux are mixed evenly, placed in a crucible, placed in a crystal growth furnace, heated to 800-1500° C., kept warm for a certain period of time, cooled to 800-850° C. in two stages, and finally cooled to room temperature; Then, the crucible containing the mixture of terbium iron borate crystals and flux is immersed in hot dilute nitric acid and subjected to ultrasonic vibration to separate the terbium iron borate crystals.

4. The method for preparing a multifunctional terbium iron borate magnetic refrigeration crystal material according to claim 3, characterized in that: The terbium-containing compound A is a terbium-containing oxide; the iron-containing compound A is an iron-containing oxide; and the boron-containing compound is a boron-containing oxide.

5. The method for preparing a multifunctional terbium iron borate magnetic refrigeration crystal material according to claim 4, characterized in that: The terbium-containing compound A is selected from Tb4O7, the iron-containing compound is selected from Fe2O3, and the boron-containing compound A is selected from B2O3.

6. The method for preparing a multifunctional terbium iron borate magnetic refrigeration crystal material according to claim 4, characterized in that: In step (1), the terbium-containing compound A, the iron-containing compound, and the boron-containing compound A are mixed according to a molar ratio of atomic Tb, Fe, and B of 1:3:

4.

7. The method for preparing a multifunctional terbium iron borate magnetic refrigeration crystal material according to claim 4, characterized in that: The flux used in step (2) is composed of a boron-containing compound B, a terbium-containing compound B, and a bismuth-molybdenum compound in a molar ratio of 15:3:5; The boron-containing compound B is selected from B2O3, the terbium-containing compound B is selected from Tb4O7, and the bismuth-molybdenum compound is selected from Bi2Mo3O 12 .

8. Use of the multifunctional terbium iron borate magnetic refrigeration crystalline material according to claim 1 or 2, or the multifunctional terbium iron borate magnetic refrigeration crystalline material prepared by the preparation method of the multifunctional terbium iron borate magnetic refrigeration crystalline material according to any one of claims 3 to 8 in the field of magnetic refrigeration, characterized in that: The multifunctional terbium iron borate magnetic refrigeration crystal material is used as a magnetic refrigeration material at an ambient temperature of 2-60K.

9. The use according to claim 8, characterized in that Below 35K, it is used as a magnetic refrigeration material in the heat dissipation of electronic devices; or below 60K, it is used as a magnetic refrigeration material in rotary magnetic refrigerators.

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